


The Next Day

by verycherryskeleton



Category: Undertale (Video Game)
Genre: Biting, Dirty Talk, Fellcest - Freeform, Fontcest, M/M, Masochism, Pining, Smut, Vaginal Fingering
Language: English
Status: Completed
Published: 2018-12-03
Updated: 2018-12-03
Packaged: 2019-09-06 12:28:24
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,335
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/16832617
Author URL: https://archiveofourown.org/users/verycherryskeleton/pseuds/verycherryskeleton
Summary: UF Sans x UF Papyrus. (Fellcest).It's the day after their first time~





	The Next Day

Sans flinched as he sat on the stool in Grillby’s, trying to find the least painful angle to rest on. Grillby wandered over and placed a bottle of mustard in front of him, arching his brow at Sans’ flinching.

“Heh, fell out of bed last night Grillbz. Don’t worry.” He waved him off and started sipping on his bottle as Grillby walked away to serve someone else. Sans sighed internally in relief. Him and Boss had finally took things to the “next level” last night and they might have gone a bit overboard in their excitement… He didn’t want anyone to catch on to his condition. He certainly didn’t want people finding out about their relationship, especially now that they had got so far.

Predictably the bar started to fill up with the usual’s. Sans shifted in his seat with worry, he really didn’t want people to know he was hurt at all. If that news spread around, some monsters might think he was an easy target. While he could still defend himself simple enough, he really didn’t want to go through the effort of a fight right now. He didn’t need any more pain.

Granted, he could just go back home and avoid prying eyes, but if he did he knew Boss would fuss over him and worry he’d gone too far. It DID hurt but last night was amazing and he didn’t want Boss thinking he had to be gentle with him. He’d repeat THAT again and again even if it meant he had to suffer for it later. 

Sans came back to himself and noticed that he was sweating and blushing. Shit he had to stop thinking about it or the situation would become even more embarrassing.

Eventually Sans decided to take a walk over to Waterfall where he could find some relative peace. The place was often pretty secluded and there were a few areas he knew of that were hidden away that others didn’t seem to know about. Maybe he could go and have a nap there for a while… He’d teleport but his magic was still a little drained, but perhaps the walk would do him some good. He needed to get his muscles moving again.

With his mind made up, he downed his bottle of mustard and ordered a burger to go. Once Grillby gave him his order, he bid him goodbye and started to head off, wincing as he tried to keep his walk steady.

—-

He arrived into Waterfall without too many incidents, except a few dogs sniffing around that he managed to bypass. He finally made his way to his favourite spot and sat on the bench situated there, taking a deep, steadying breath as the relief washed over him. He couldn’t stay here for too long or else Boss would get worried, but he appreciated the moment of privacy while it lasted. He smothered his burger in some mustard he kept in his jacket pocket and ate half of it in one go.

While he was chewing on his second bite, he heard some voices a short distance away. 

Was that giggling? He didn’t think he’d ever heard that kind of friendly laughter in the Underground before… Sure some monsters were civil with each other to convey they weren’t enemies and were safe company… But this giggling and hushed, lighthearted conversation was something he’d never heard in public before. It was unsafe to show you had attachments to another monster like this.

After listening for a few more moments, his curiosity got the better of him. He wanted to see who these monsters were. Maybe he could use it against them. He wasn’t one to manipulate people if he could help it, but it was always good to have something to hang over someone if something bad were to happen. You can’t be too careful when you live in a place like this. 

He waited until the voices had faded away and he knew the coast was clear, then left his spot without them seeing him, speeding his walk to catch up with them again.

When the voices started to increase in volume, he turned a corner and saw none other than the second in command of the Royal Guard, the closest person Papyrus could call a friend, as well as the Royal Scientist, grinning at each other in mirth. The scientist even had a small blush adorning her yellow scales. 

Sans smirked.

Perfect.

“You two seem to be enjoying yourselves.” Sans snickered behind them, causing them both to jump up in alarm and turn around quickly to see who had caught them. When Undyne saw who it was she crossed her arms and gave him a cold smirk.

“What’s it to you punk?”

“Oh nothing…” He replied smugly. “I just didn’t know you two were so close… Though, I’m not sure anyone else does either…”

He shoved his hands into his jacket pockets and winked at them, to which he could see Undyne fuming and Alphy’s sweating and giving him a hard glare.

That was until Sans took a step closer to say something else and accidentally moved his joints quicker than he intended, causing him to wince as a hot sting of pain lanced through him. He quickly tried to hide his wince and set his face back to his care-free smirk but it was too late, both of the other monsters had saw it.

“What’s wrong Sans?” Now it was Undyne’s turn to grin. “Exerting yourself too much? The last time I saw someone with joints that painful was when I had a particularly bad sparring session with your brother…”

At the mention of Papyrus, Sans blushed a deep burgundy before he could stop himself. He swore inwardly as Undyne’s grin only grew wider.

“You been getting into some fights lately? Or any other PHYSICAL activities…?”

Both Alphy’s and Undyne burst out laughing at that as Sans sunk half of his face into his jacket in embarrassment. Stars he’d really screwed this up, now those two would have something even worse over him.

“What are you two talking about?” Sans hoped he could somehow lie his way through this.

“It’s just that, I saw your brother earlier and he seemed to be in a VERY good mood for someone who usually looks like he wants to kill every monster he meets.” Undyne snickered. “And funnily enough, he blushed at the mention of you too. I usually wouldn’t peg Papyrus as the blushing type but I guess some topics are an exception…” That led to another spurt of laughter.

Flashes of Papyrus’ flushed face as he pinned his brother against his bedroom door sprung to Sans’ mind and heat pooled at his pelvis. Shit, shit, shit. 

“Can we pretend that this conversation never happened?” Sans begged, barely disguising the hint of desperation in his voice.

The two monsters had yet to stop laughing and only nodded as tears started to roll down their faces. Sans vaguely recalled some patronising smooch noises as he quickly teleported back home to hopefully never leave the house again.

–

When he popped into the main living area of his home he found that Papyrus was in the kitchen cooking some dinner for the both of them. He started to creep up the stairs hoping his brother wouldn’t hear him but a squeak from the staircase gave him away. He heard the clink of cutlery pause.

“Sans, is that you?”

Sans paused and contemplated running to his room and locking the door, throwing some flimsy excuse about not feeling well, but Papyrus had already walked out of the kitchen.

“Uhh… H-hey Boss…” Sans stuttered. Seeing his brother sweating and wearing his loose tank top was really not helping. His magic was already starting to form at his pelvis.

“Are you okay Sans? You look really hot. Do you want me to get you a glass of water?”

That actually did sound really appealing right now.

“Sure Boss, that would be great.”

He hastily went to sit on the couch so he could use the cushions to disguise the problem in his shorts, the heat of his arousal almost visible through them, but he winced again as he did so, alerting Papyrus immediately. Damn his brother’s perfect perception and instincts.

“Sans! What’s wrong, are you hurt?” Papyrus ran straight to the couch and fussed over Sans worriedly, checking him over for any injuries. In doing so, he noticed the heat radiating from Sans’ shorts and barely suppressed a smirk.

“It’s fine Boss, I’m still just a little sore from yesterday. But it’s n-no big deal I promise!” He blushed and tried to hide himself inside his jacket again. This day couldn’t have gone any worse.

Papyrus lifted Sans up and placed him on his lap as he sat himself down on the couch.

“Oh, I see… I guess that means I shouldn’t take care of this then…” Papyrus proceeded to rub at Sans’ clothed pelvis, causing Sans to moan loudly.

“Boss please! Don’t mess with me!” He begged, shifting his hips closer to Papyrus’ hand.

Papyrus couldn’t help his smirk this time, using his other hand to stroke up Sans’ spine and along his bottom ribs.

“I don’t know… you’re clearly still sensitive from yesterday….” Papyrus teased, proving his point by rubbing at his crotch more firmly, eliciting a loud cry out of his brother, as well as some fresh tears falling out of his sockets. However, Sans only pressed into the touch more.

“Boss… please… I’ll do anything!” Sans sobbed. “I want you so badly… please!”

Papyrus growled and leaned down, capturing Sans’ mouth in a rough kiss. Sans was the first to conjure his tongue, pressing it against Papyrus’ teeth in his desperation to taste his brothers magic again.

Papyrus complied, pushing his own tongue into Sans’ mouth as he pulled his shorts down and to his ankles.

“I didn’t realise fucking you once would turn you into a needy whore.” Papyrus growled lowly, his cock hardening as he felt the wetness of Sans’ already conjured mound. “And while you’re still sore from last time too. What am I going to do with you Sans?”

At that Papyrus shoved one of his phalanges inside of his brother, thrusting it while his other hand clawed at his femurs. He could feel Sans shivering against him, whimpering his name.

“Such a naughty boy, making me want to fuck you like this. I hope the pain reminds you of what you made me do.”

Papyrus shoved in another phalange as he started to unbuckle his belt, freeing his hard member as he stopped his thrusting and rubbed at Sans’ clit.

Sans couldn’t even form words anymore, his desperation leading him to rut into Papyrus’ hand and pull at the straps of his brother’s tank top, tears still leaking down his face. Papyrus couldn’t hold on anymore either, rubbing at his brother’s lips with his cock as he felt the wetness cling to the head of his dick. Papyrus groaned and canted his hips a little at the feeling.

“You going to ride me Sans? Do you want to feel my long, hard cock inside of you?” Papyrus then proceeded to bite down hard on Sans’ clavicle, eliciting a high-pitched moan.

“Pl-please….” he gasped brokenly, the mingling of pain and pleasure proving to be too much as Papyrus licked at the bite.

Before he could retort, Sans screamed as he pushed himself down on his brothers cock at the same time Papyrus thrusted inside, pushing himself deeper than he intended. It took them both a few seconds to recover, breathing heavily as they clung to each other. Once Papyrus gathered his thoughts again, he started to thrust into Sans steadily, only quickening his pace when he was sure Sans had recovered enough to take it.

Each thrust elicited a sharp sting from Sans’ sore bones as he was pounded, but that only enhanced Sans’ pleasure as his brother hit that spot over and over again. He rocked his hips back and forth on his brothers lap as Papyrus reached down and rubbed at his clit again while he continued to thrust inside of him. 

Before long the pleasure became too much to bare, and Sans could feel himself clamping down on his brother’s dick as heat started to pool at his pelvis.

“Boss… I’m gonna… AH-HH PAPYRUS PLEASE I NEED…” Sans wailed.

“Cum for me Sans.” Papyrus purred, cutting him off.

Sans arched up and screamed his brother’s name as his pussy clamped down hard around his cock, causing Papyrus to curse under his breath and grunt as he shot his load deep inside his brother, spurt after spurt hitting the back of his conjured magic, some of their cum spilling out and dripping down Sans’ femurs.

Sans went limp on his brothers lap as they both recovered their breathing. He smiled as the pain and pleasure mingled in his afterglow, feeling utterly content. After a minute Papyrus lifted him from his lap, adjusted his clothing and went into the kitchen. 

He came back a few minutes later with a wet washcloth and a glass of water. He washed off his brother’s bones and then forced Sans to drink from the glass. After he was done, he grabbed the blanket folded on top of the couch and placed it over his brother, kissing him softly.

“I’m fine Boss, no need to fuss…”

Papyrus cut him off again.

“You won’t move from this spot until you’ve recovered enough to walk again, I’ll go finish making dinner. And this time, I want to make sure you don’t go out until you’re no longer in pain. 

He huffed in annoyance but couldn’t hide his small smile. Sans would never allow him to look after him. He expected Sans to argue again but instead Sans mumbled affectionately, already falling asleep; 

"Heh, I love you Boss.”

Papyrus’ soul jumped in his chest. 

“I love you too Sans.”


End file.
